refactored session's interaction with engine/connection

  - follows law of demeter
  - Table.engine uses AR::Base adapter

1 files changed, 48 insertions, 0 deletions

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+todo:
+- clarify distinction between engine and connection: an engine is a connection pool, plus the quoting operations
+- #relation is now on scalar, attribute and relation; you must admit it's name is confusing given that e.g., relation already has a strategy (Sql::Relation) ... should it be called predicate strategy? operand1.to_sql(operand2.predicate) maybe prefer operand1.cast(operand2) or project or in light of
+- clean up integration tests in join - i find the aggregate stuff too integrationy; unit testing would be better
+- test relation, table reset
+- cache expiry on write
+  - rewrite of querycache test in light of this
+- relation inclusion when given an array (1,2,3,4) should quote the elements using the appropriate quoting strategy taken from the attribute
+  - descend on array, along with bind written in terms of it
+- standardize quoting
+  - use strings everywhere, not symbols ?
+- rename and test sql strategies
+  - the parallel names are confusing since it's not obvious what's what. plus, we lack unit tests; the biggest complaint is a lack of clarity concerning what purpose these serve in the system. Unit tests wont illustrate much unless we use concrete examples.
+- rename the tion (Selection) classes so that words that don't end in tion don't seem inconsistent
+- re-evaluate bind
+
+done:
+. Relation <=> Relation -> InnerJoinOperation
+. Relation << Relation -> LeftOuterJoinOperation
+. InnerJoinOperation.on(*Predicate) -> InnerJoinRelation
+. LeftOuterJoinOperation.on(*Predicate) -> LeftOuterJoinRelation
+. Relation[Symbol] -> Attribute
+. Relation[Range] -> Relation
+. Attribute == Attribute -> EqualityPredicate
+. Attribute >= Attribute -> GreaterThanOrEqualToPredicate
+. Relation.include?(Column) -> Predicate
+. Relation.project(*Column) -> ProjectionRelation
+. Relation.select(*Predicate) -> SelectionRelation
+. Relation.order(*Column) -> OrderRelation
+. #to_sql
+. Remove Builder
+. Namespace
+. Audit SqlAlchemy for missing features
+- Generalized denormalizations on any aggregation (count, yes, but also max, min, average)
+- Remove operator overloading of << and <=> for joins. Make it just foo.join(bar) and foo.outer_join(bar).
+- Remove operator overloading of == for predicates. make it a.equals(b) (note lack of question mark).
+- hookup more predicates (=, <=, =>)
+- get some basic aggregations working: users.project(user[:points].max)
+- Alias Table Names
+- When joining with any sort of aggregation, it needs to be a nested select
+- get a scalar select working: users.project(users[:name], addresses.select(addresses[:user_id] == users[:id]).project(addresses[:id].count))
+- Session
+- sublimate scalars to deal with the fact that they must be quoted per engine
+- clean-up singleton monstrosity
+- extract hashing module
+- hash custom matcher
+- make session engine stuff follow laws of demeter - currently doing some odd method chaining? rethink who is responsible for what
+  - session just calls execute, passing in a connection; by default it gets a connection from the relation.